The invention relates to a roller device that is designed to maintain and improve concentricity.
It is often crucial that rollers used in a variety of machining processes have working circumferences that are highly concentric. A xe2x80x9crolling devicexe2x80x9d need not only include devices whereby a web-shaped product is treated in interaction with a counter-roller, i.e., between two rollers. There are also cases where only one roller interacts with a fixed counter-element For example, in a system for ultrasound treatment of a web, a moving roller works together with a sonotrode that is radially directed towards it, and the web, which is to be bonded or cut is passed between the two. An example of such an arrangement is described in DE 198 13 121 C1.
An example of a typical roller device, with a heated roller, is known from European Patent 813 632. A heating device is arranged in a cylindrical recess of the roller body, which device serves to increase the temperature at the working roller circumference and thereby to directly influence the treatment of a web that is conducted using the roller. The goal of the known heated roller is to achieve the most uniform possible heating crosswise to the web, i.e., over the length of the roller. For this reason, so-called xe2x80x9cperipheralxe2x80x9d bores are provided in the roller body, parallel to the axis, located radially outside of the recess. The bores are partially filled with heat carrier fluid and connected with one another at the ends by annular chambers. The heat carrier fluid condenses at colder spots of the peripheral bores making the temperature in the channel system more uniform. Heating takes place in order to bring the roller to a certain temperature that deviates from the ambient temperature, which temperature is practical for the treatment to be conducted.
It is known in the art for it to be possible to adhere to a concentricity tolerance of 5 xcexcm at roller lengths of 2 to 3 m. However, even this accuracy is sometimes not sufficient for a uniform bonding process, and can be the cause for the variations in properties of the finished product. Furthermore, any irregularity that is present tends to become more pronounced in operation. In an ultrasound treatment, when a beat defect moves past the sonotrode, the output transferred to the nonwoven increases at this point on the circumference of the roller, and results in a greater amount of heat introduced into the nonwoven. This results in the non-uniform bonding effect and also results in an increase in the amount of heat transferred to the roller in this circumference region. This in turn results in a preferential temperature increase of the roller in the direction determined by the location of the beat defect, and thereby in an increase in the non-concentricity. The variation in the bonding effect therefore increases on its own over the course of operation.
Non-concentricity on the order of 5 xcexcm, as indicated, is not only attributable to tolerances that exist from the start. Such non-concentricity can also occur later, for example if the roller is given a non-uniform temperature in production, due to some external cause. Even the mere influence of the roller weight itself, when the roller is not moving, can be the cause of slight structural changes that are initiated as a result, leading to non-concentricity on the order indicated, which will increase and build up under the influence of the ultrasound energy transfer.
Thus, in the case of ultrasound treatment systems, the requirements concerning concentricity of the roller are particularly high. This holds especially true for ultrasound bonding of nonwovens made of thermoplastic fibers. Here the ultrasound generator works via the fixed sonotrode, i.e., the ultrasound transmitter, radially against a roller that forms the so-called counter-roller, which carries the bonding pattern in the form of a surface engraving. At the raised parts of the surface engraving, the transfer of ultrasound energy to the nonwoven is particularly intensive, so that here, a preferential temperature increase and preferential melting of the fibers occurs, and in this manner, bonding of the individual threads or fibers of the nonwoven takes place at certain points or along certain lines, in accordance with the pattern, thereby bonding the nonwoven layer.
Even the slightest variations in the distance between the fixed face surface of the sonotrode and the circumference of the moving counter-roller result in a difference in bonding effect. Such a nonwoven demonstrates varying properties that vary with the rhythm of rotation of the counter-roller. For example, this can result in a finished product with a differing feel.
The irregularities as described exist in the circumference direction of the roller, not in the lengthwise direction. If there are temperature differences over the length, these can be combated with the device according to European Patent 813 632, for example, but this device is ineffectual when there are differences in the circumference direction.
The present invention, on the other hand, deals with those deviations that result in bending of the roller body in a plane that passes through the axis, in that the roller body has a slightly higher temperature on one lengthwise side than on the opposite lengthwise side; in this case, it bends like a bimetallic strip, in that the one lengthwise side expands, but the other does not.
However, the effect is not tied to the fact that different temperatures prevail at the opposite lengthwise sides, right from the start. The starting situation for bending that causes non-concentricity can also be a finishing inaccuracy or a structural change, as already mentioned.
The effect to be combated with the invention must also be kept separate from the question whether or not this is a heated roller. The problem according to the present invention can occur both in a heated roller, where any slight temperature differences in the circumference direction are superimposed on the general heating of the roller, and in entirely unheated rollers, where the differences come about as a result of the non-uniform energy introduction of an ultrasound system, for example.
Proceeding from the problems in the ultrasound bonding of nonwovens as described, the present invention is based on the task of maintaining the greatest possible concentricity of a roller in operation.
This task is accomplished by the present invention which provides a roller device that has a roller. The roller has a cylindrical roller body that forms a working roller circumference of the roller. The roller is rotatably mounted at its end. Also provided is a tempering system assigned to the roller body. The tempering mechanism extends over the length of the roller body and configured to adjust the basic temperature of the roller. An equalization system is provided for preferentially tempering the roller body in a narrow circumference angle region adjacent to a plane that passes through an axis of the roller body.
The means of equalization can fundamentally be a heating means or a cooling means. It is preferred that heat transfer to the roller takes place in a certain direction, seen in the circumference direction, so that the moving roller is non-uniformly heated or cooled, in targeted manner, but not over its length, rather in the circumference direction. With this heat transfer, which takes place only in one direction, i.e., in a zone that is essentially flat or maintains a narrow circumference angle, undesirable lengthwise bending of the roller and the non-concentricity that results from it can be counteracted via the corresponding thermal expansion that is achieved. The bimetallic effect should be canceled out. Therefore, if there is a certain xe2x80x9cbeat defect,xe2x80x9d its effect on the circumference of the roller can be reduced, according to the present invention, by heating the opposite side or by cooling the same side. The temperature differences that must be brought about for this purpose amount to only a few degrees, and have nothing to do with the significantly greater temperature differences that are required for normal heating of the roller.
The system can be configured for use in ultrasound treatment systems where very stringent requirements with regard to concentricity are found. In an ultrasound treatment system webs using a sonotrode directed radially against the roller circumference.
The tempering system can, at the same time, be the equalization system. Thus, the equalization system do not have to form a system separate from the tempering system.
The equalization system can be structured in oblong, rod shapes, and be arranged continuous over the length of the roller, parallel to the axis, or distributed uniformly over the circumference. In other words, their structure is similar to that which can be the case for the tempering system responsible for total heating or cooling.
A design structure of the roller device can be a cylindrical recess that is coaxial to the roller circumference at least over a significant part of the length of the working roller circumference. The equalization system are arranged in the interior of the recess. The equalization system can be formed to move with the roller.
However, the system can also be arranged in the interior of the recess so that it does not rotate. Instead it can be activated or deactivated with the rhythm of rotation of the roller. Every time that the xe2x80x9ctarget zonexe2x80x9d passes by, the tempering system are therefore switched on, and shut off again immediately afterwards. In this manner, too, preferential heating or cooling of a zone of the roller, delimited in the circumference direction, can be brought about.
Several rod-shaped tempering elements that are parallel to the axis can be provided. These elements can be distributed over the circumference, move with the roller, and can be controlled separately. The roller can have a device for determining the angle location of a concentricity defect assigned to it. Such a device can be linked with a control device, in such a way that the concentricity defect can be countered by individual control of the tempering elements, depending on the location of the concentricity defect.
The roller can be provided with a cylindrical core that has axis-parallel grooves for the tempering elements on its outside circumference.
A set of slip rings can be connected to rotate with the roller, where electrical energy can be supplied separately to the individual tempering elements, using this set of slip rings.
An individual tempering element can be preferentially activated by using corresponding metering of the electrical energy supplied to an individual tempering element, in order to counteract the non-concentricity. For instance, the electrical tempering elements can be activated directly, using the electrical energy supplied to them. In this case, the elements can be electrical heating rods, for example, or cooling rods operated by system of Peltier elements. In another embodiment, a separate feed of the electrical energy is combined with the channels, in that throttle devices that are arranged in the channels can be activated using the electrical energy. These throttle devices influence the flow-through cross-section for a heat carrier medium and therefore the heat transfer output.
In the embodiment described above, several separate rod-shaped tempering elements are provided, distributed over the circumference of the roller.
In another embodiment, the recess has a heat carrier medium flowing through it, which forms the tempering system (which therefore do not necessarily have to be a rigid object). The flow is made non-uniform over the cross-section of the recess, on one side, which also has the result of a targeted, non-uniform heat transfer in the circumference direction, and, in this case, forms the equalization system. Making the flow non-uniform is sufficient to achieve the effect according to the invention, because the required temperature differences amount to only a few degrees.
Making the flow non-uniform can be achieved by a rod-shaped displacement body arranged in the recess, which rotates with the roller, parallel to the axis of the recess; this displacement body can be shifted parallel to itself, in the cross-section of the recess, away from the center. The location of the displacement body in the recess can therefore be adjusted in the circumference direction, depending on the location of the beat defect, and/or adjusted in the radial direction, in order to influence the strength of the effect.
This can be implemented, in terms of design, by having a rod-shaped displacement body guided, at its two ends, in eccentric arrangements that rotate with the roller and can be adjusted in terms of angular position and, if necessary, eccentricity.
In accordance with another embodiment the rod-shaped tempering elements can be formed by a spray pipe through which a fluid heat carrier medium flows, parallel to the axis of the roller, with a linear exit zone that extends along the spray pipe on one side, through which the heat carrier medium can be sprayed out essentially in a plane that goes through the axis, from the inside of the spray pipe against the inside circumference of the recess of the roller body, i.e. against the outside circumference of the body. In one system, the exit zone can be formed of a row of holes, jets, or slits parallel to the axis of the spray pipe. It is practical if the spray pipe, if it is arranged in the recess, is structured so that it can be displaced in the cross-section of the recess, and rotated around its own axis, in order to be able to hit a certain position of the inside circumference of the recess, determined by the position of the beat defect, with the heat carrier medium that is sprayed out.
The effect of the tempering element that serves as an equalization element can be activated and deactivated using a shutter.
In the embodiments described above, the equalization system are provided in a recess of the roller body, i.e. in its interior. It is also possible, however, to arrange the equalization system outside the circumference of the roller body, adjacent to it, and to activate and deactivate them with the rhythm of rotation of the roller. In this case, the required thermal influence on the roller body takes place not from the inside, but rather from the outside. Activation and deactivation during each rotation or after several rotations is necessary, so that the thermal influence is restricted to a certain zone that takes up a small circumference angle, which zone is supposed to bring about the counter-effect to the beat defect that exists in the roller.
The tempering device can also be arranged outside of the roller can be at least one fixed, oblong, axis-parallel tempering element that extends essentially over the length of the roller body.
The drawing schematically shows exemplary embodiments of the invention.